I. Field of Use
The present application relates to the field of network communications. More specifically, the present application relates to optimizing Over-the-Top Services that operate over carrier networks.
II. Description of the Related Art
Today, a number of VoIP services exist for PCs and phones. In general, these services work very well for voice, video, and data sharing when both users are using fixed-line DSL/cable infrastructure (or indirect via WiFi) since IP addresses do not change, bandwidth is relatively abundant, radio issues do not exist, and latency is low.
Over-the-Top services refer to services that run over a network, but that are not offered by an operator of the network. It is often referred to as “over-the-top” because these services ride “on top” of the service already provided by the network operator and don't require any business or technology affiliations with the network operator. An example of an OTT service is the Skype® VOIP communication service, which allows users to place VOIP calls, often for free.
To date, most Over-the-Top (OTT) VoIP services have simply moved their stationary home/office solutions directly to mobile devices. However, the user experience can become very poor (call drops, high latency, poor audio quality) when traditional best effort WAN-based data connections become congested on cellular networks. This is caused by the constantly changing radio conditions of both WiFi and carrier infrastructure and competition from carrier grade services like carrier voice to best effort data solutions.
Over the last 30 years, the wireless industry has created sophisticated metro-area networks allowing a single voice call to be handed off from cell-tower to cell-tower, depending on certain conditions. Over time, a data overlay (GPRS/EDGE) was created to allow data (initially text message and today internet pages to movies) to travel on the same network, but typically with lower priority to voice traffic which has a higher quality of service network guarantee. Later standards increased data rates and modulation standards, but continued voice with priority and data as a best-effort model. Today, the industry supports three concurrent networks for GSM (2G—GSM/EDGE, 3G—UMTS/HSPA+, and 4G—LTE) and two for CDMA (CDMA 1×RTT to CDMA EV-DO Rev B). Carrier networks handover devices between these standards, even while in a single call. In addition to current cellular networks, new cellular standards are also evolving to allow interoperability for both data and voice with 802.11 (WiFi) networks. In this case, phones and other mobile devices can connect either to the standard Internet backbone for best effort data or to new servers located at a carrier's premises to support carrier services (like voice and text) over WiFi.
Over the Top (OTT) services have been developed that allow information such as voice, text, presence, video chat, file sharing, etc. to be provided to users who have PCs, mobile handsets, or game machines with internet connections (whether WiFi or cellular). Often without cost (WiFi based), services like Skype are available to authenticate oneself and find active users to connect to. Once active IP addresses have been exchanged between clients, users can often complete a session (like a voice call) with minimal involvement by the service (NAT transversal). To date, most OTT services have been used on stationary terminals leveraging DSL or cable backhaul services. Since these commonly provide a static or session IP, have significant backhaul bandwidth, and do not suffer radio issues, many OTT sessions occur with limited to no quality issues.
Moving this OTT capability to mobile clients has proven difficult as both WiFi and cellular services have inherently varying signal conditions, especially while mobile (from walking to moving in a train or car). In WiFi circumstances, bandwidth is often good (except with many users sharing an AP or when some users have significant bandwidth demand—i.e. video streaming or with limited backhaul bandwidth), but signal conditions can vary dramatically at the edge of the access point signal range. Thus, full loss of signal or significant packet drop-out can occur as one goes far (50 to 100 m) from the access point. Note that obstacles such as walls and floors in a home with a single WiFi AP can also cause rapid changes in signal quality when the user moves around.
The issue in a cellular network is a combination of radio losses and carrier network control of resources. For the first, good cellular network design will try to provide at least voice coverage everywhere except deep in buildings/underground or in low-population density areas. A complex system of carrier network coordinated hand-offs between multiple towers and small cells also provides seamless hand-off of users as they move between coverage radii of various towers. However, network resource control prioritizes carrier services like voice above best effort services (like traditional browser or streaming data). Thus, in situations near the cell edge, periods of high congestion, high traffic, or poor tower backhaul, the network manager can force a user's best effort services to be degraded or temporarily suspended.
In summary, trying to provide OTT services on best effort networks (especially services like voice OTT services where customers expect fairly reliable continuous voice streaming) can be challenging at best.